IB Environmental Systems and Societies

1. Topic 4
Water and aquatic food production
systems and societies
4.3 Aquatic food production systems

2. Aquatic Food Production
• Algae – human food source, agar gels
(around 30 million tonnes/yr
harvested, largely in SE Asia)
• Fish – human consumption,
animal/pet food, fish oil, food for
aquaculture, gelatin, fertilisers (approx
20kg/capita/yr worldwide and
increasing)
• Shellfish – mollusks (e.g. scallops),
crustaceans (e.g. shrimp, lobsters)
• Others – reptiles (e.g. turtles,
crocodiles, alligators), amphibians (e.g.
frogs), mammals (e.g. whales,
dolphins, seals)

3. Food Prices
• World food prices have been
increasing recently
• There is increasing meat and
fish consumption in MEDCs
and LEDCs
• More staple crops and fish
are being used as animal feed
• Also more farmland is being
used to grow biofuels
(especially in Brazil) - Land is
becoming more expensive and
more limited
• World oil prices are unstable
and transportation costs are
therefore increasing
World Food Price Index

4. Terrestrial and Aquatic Systems
• In MEDCs we generally want a large variety of foods, and
this also gives a more healthy diet
• This is leading to greater demand for meat and fish
• Also driven by rising human population and changes in
population demographics
• Terrestrial farming (e.g. arable and herbivore farming)
harvests low trophic levels
• Aquatic farming (e.g. fish farming) generally harvests high
trophic levels
• The Second Law of Thermodynamics shows that more
energy must be put into an aquatic system to harvest the
same amount of biomass

5. Terrestrial and Aquatic Systems

6. Sea Fisheries and Sustainability
• Mostly occurs near the coast. Bigger stocks since more nutrients available from
river discharge and upwelling (caused by strong winds and coastal currents)
• Fisheries are only sustainable if the rate of removal < growth rate
• However, most major fisheries are now over-exploited
• The maximum sustainable yield occurs where population is increasing at its
maximum rate
MSY
Above MSY, yield is reduced by
competition for resources
Below MSY, yield is decreased due
to the small population
Fishing techniques

7. Sea Fisheries and Sustainability
• There are 2 major problems which prevent
global sustainability:
– The Tragedy of the Commons – Every country (and
individual fishermen) wants to catch fish in their
own territorial waters before the stocks leave and
head to those of another country.
– Short-term gain – It is easy (and tempting) to see
the greatest gain over the short term rather than
look towards long-term conservation of stocks

8. Sea Fisheries and Sustainability
• Possible conservation strategies include:
• Reduce the size of fishing fleets
• Reduce the size of individual fishing boats
• Reduce net/mesh size (this helps to prevent
juvenile fish being caught which can then spawn)
• Closed seasons
• Exclusion zones/Marine Protective Areas (these
conserve habitats and allow fish to spawn)
The Downeaster Alexa

9. Case Study 1 - Newfoundland
• Before 1950, the largest cod stocks in the world
• From 1950s onwards introduction of technology
to exploit the stocks commercially
• Fishing peaked in 1968 – 800 000 tonnes
• The local and national government did not
intervene for fear of affecting jobs
• The entire fishery collapsed
• In 1992 it was closed completely, leading to the
loss of 42 000 jobs
• It still hasn’t recovered
Newfoundland cod fishery collapse

10. Case Study - Newfoundland

11. Case 2 - Iceland
• Most important industry in the country is cod fishing
• Stocks began to decline in the early 1950s, but the
government decided to take action
• They protected and expanded their territorial waters
aggressively. This lead to confrontations with the British
Navy between 1952 and 1976 (The ‘Cod Wars’ *)
• Restrictions were introduced on fleet size, boat sizes,
fishing gear and mesh size
• Introduction of closed seasons
• Use of coast guard and inspectors to enforce restrictions
* Won by Iceland after it threatened to leave NATO The Cod Wars

12. Marine Hunting
• Includes hunting of seals, dolphins and whales
• In the Western World this is largely seen as
unethical
– Marine mammals seen as intelligent and close
relatives of humans
– Many hunting methods seen as causing unnecessary
pain, e.g. harpooning or clubbing
– Some species have been driven close to extinction
– Hunting of fur seals involves killing juvenile animals
• However hunting may play an important role in
many indigenous communities, e.g. Inuit

13. Aquaculture
• This is the farming of aquatic species (marine and
freshwater)
• Not just as a food source. Also for commercial
products, pets, skins etc.
• Fish, shellfish, reptiles and amphibians all farmed
• Aquaculture is increasing as fisheries are declining (due
to over-exploitation)
• Includes open systems and closed systems
• Open systems are created by caging species in an
existing habitat (riverine or coastal)
• Closed systems are created in tanks situated inland

14. Environmental Impacts of Aquaculture
• Loss of habitats, e.g. mangroves, to be replaced with closed
systems (e.g. caged fish or shrimp)
• Generation of sediments (from faeces), smothering benthic
habitats and creating anoxic conditions
• Generation of nutrients (from faeces) creating algal blooms
and eutrophication of freshwater
• Contamination of with antibiotics and hormones
• Pollution caused by antifouling paints which contain toxins
including heavy metals
• Spread of disease in densely-packed populations
• Escape of farmed animals (may outcompete or prey on
indiginous species)
• Attraction of predators which may become trapped in cages